To enhance impact resistance and chemical resistance of a thermoplastic resin, an impact modifier containing rubber component has been added to produce a resin. As an impact modifier, methyl methacrylate-butadiene-styrene (MBS) resin, ethylene chloride (CPE) resin and acrylic resin have been generally used. However, high industrial development asks better impact modifier having improved impact strength, weather resistance and chemical resistance than the conventional impact modifier. Thus, a silicone impact modifier has been developed, which seems to have improved impact resistance resulted from the very low glass transition temperature of −120° C. It has been reported that when the silicone impact modifier is copolymerized with acrylic rubber, dispersibility of the resin is improved, resulting in the enhancement of weather resistance and impact resistance.
U.S. Pat. No. 4,994,523 describes that a silicone-acrylic impact modifier having excellent impact resistance and weather resistance is produced by the steps of polymerizing silicone polymer with acrylic rubber monomer and grafting aromatic monomer, cyan monomer or alkyl(metha)acrylate monomer onto the above produced polymer.
Korean Patent Publication No. 2002-0075901 describes that impact resistance of a resin can be greatly enhanced by polymerization of vinyl monomer in the presence of latex mixture of silicone rubber latex and acrylic rubber latex.
Korean Patent Application No. 2003-0092273 describes that a silicone-acrylic impact modifier having improved impact resistance, colorability and chemical resistance is produced by grafting aromatic monomer or non-aromatic monomer onto silicone rubber and then grafting acrylic rubber thereon, increasing the grafting efficiency of acrylic rubber.
Korean Patent Publication No. 2000-0076255 describes that a silicone rubber graft copolymer is produced by graft-polymerization of vinyl monomer on silicone polymer with narrow particle diameter distribution attributed to polymerization of silicone rubber in vinyl copolymer emulsion.
Although a thermoplastic resin composition containing such silicone-acrylic impact modifier has satisfactory low-temperature impact strength and weather resistance, the resin is limited in use because of poor pigment-colorability generated by the silicone rubber component.